Latching-type digital phase shifter employing toroids of gyromagnetic material



Nov. 28, 1967 J. BROWN, JR. ETAL 3,355,683

LATCHINGTYPE DIGITAL PHASE SHIFTER EMPLOYING TOROIDS OF GYROMAGNETIC MATERIAL.

Filed Oct 21, 1965 2 Sheets-Sheet 1 DEMAGNETIZ ING WINDING INVENTOR. JUL /A/V BROWN JR DOA/4L0 R. TAFT BY ATTORNEY Nov. 28, 1967 J, R ETAL 3,355,683

LATCHING-TYPE DIGITAL PHASE SHIFTER EMPLOYING 'TOROIDS OF GYROMAGNETIC MATERIAL Filed 001:. 21, 1965 2 Sheets-Sheet 2 MAGNETIZING AND DEMAGNETIIZING CURRENT SOURCE MAGNETIZING AND DEMAGNETIZING 51 CURRENT SOURCE INVENTORS JUL M/V BROWN JR I BYDO/VALD R. mFr

QZWM 15M ATTO/P/VE)" United States Patent 3,355,683 LATfiHlNG-TYPE DIGITAL PHASE EMPLQYING TOROIDS 9F MATERIAL Julian Brown, In, Clearwater, and Donald It. Taft,

Dunedin, Fla, assignors to Sperry Rand Corporation, a corporation of Delaware Filed Oct. 21, 1965, Ser. No. 499,944 8 Claims. (Cl. 333-31) SHIFTER GYRDMAGNETIC ABSTRACT OF THE DISCLOSURE This invention relates to electromagnetic wave phase shifting devices and more particularly relates to small and efiicient reciprocal latching-type digital phase shifter that utilize toroids of gyromagnetic material whose magnetization states may be selectively switched to provide different values of phase shift and which require no external magnetizing energy to maintain the different values of phase shift. The toroids are positioned in a manner to assure optimum interaction with the linearly polarized magnetic field components of the electromagnetic waves.

Phase shifters constructed in accordance with the present invention are particularly suitable for use as the socalled digital phase shifters that have been proposed for use in radar systems whose antenna beams are to be electronically scanned. Electronic scanning is achieved by providing a plurality of wave radiating elements whose relative physical arrangement, together with their amplitude and phase of excitation, are so proportioned that the composite radiation pattern of all the elements is a shaped beam whose direction in space may be changed in a controlled manner. A rather complex waveguide network having a plurality of wave propagating paths connects the transmitter to the various radiating elements and establishes the required amplitude and phase relationships at the elements. The beam is continuously scanned in small angular increments by changing in discrete steps the phase shift of the waves through the various paths of the Waveguide network. It is obvious that in order to effectively cover a large volume of space with a rapidly scanned antenna beam, the phase shifting means in the Waveguide network must be capable of rapidly changing in discrete steps the phase of the electromagnetic waves through the various paths of the network. Further, because a large beam-scanning radar system may employ hundreds or thousands of phase shifting devices in the waveguide network, the switching power that is required to effect phase changes in all of the phase shifting devices is a matter of primary concern and must be held to a minimum.

In designing the waveguide networks for use in these types of radar systems, considerable attention has been given to the use of phase shifters that employ gyromagnetic materials. Phase shifters of the digital type employ several members of gyromagnetic material, each member having its own independent magnetizing source. Most commonly, a magnetizing source functions to mag- 3,355,683 Patented Nov. 28, 1967 netize each gyromagnetic member to one or the other of two magnetization states. Each magnetizing state produces a difierent value of phase shift and the difference between these values of phase shift is referred to as the differential phase shift. The individual member of gyromagnetic material introduce respective different values of differential phase shift, and by selectively magnetizing various combinations of the individual members to one or the other of their magnetization states, different total values of phase shift may be selected. In order to reduce the power requirements of the magnetizing sources, gyromagnetic members in the shape of toroids have been used. The toroids are characterized by having two remanent magnetization states. This then requires magnetization power only during the switching operation, and no source power is required to hold a toroid in a given one of its magnetization states. Phase shifters operating in this manner sometimes are called latching digital phase shifters.

When used in beam scanning radar systems it sometimes is desirable that the phase shifters be reciprocal, or bilateral, in their operation because in order for the antenna to receive reflected waves from the same direction in which they were radiated during transmission, the various paths of the waveguide network must maintain their same respective electrical lengths for both the transmitted and received waves. To achieve bilateral operation, the toroids of ferrimagnetic material must be positioned in the transmission lines of the waveguide network in regions where the magnetic fields of the transmitted and received waves are linearly polarized. In magnetizing toroids of ferrimagnetic material to obtain the differential phase shift from each toroid, it will not be possible to switch the magnetization states between the two remanent magnetizations of a square hysteresis loop magnetization characteristic because this would result in the same magnitude of phase shift for both magnetizations. Consequently, other combinations of magnetization conditions must be utilized in switching the toroids to produce different values of bilateral phase shift.

In order to keep the size of each phase hifter to a minimum, to minimize losses due to the fcrrimagnetic ma terial, and to minimize the energy required to switch the magnetization states of the toroids, it is necessary that the toroids be as small as possible. The maximum reciprocal differential phase shift per unit volume of a toroid is obtained when the ferrite material is properly positioned in the linearly polarized magnetic field of the electromagnetic waves and is everywhere magnetized in a transverse direction relative to the magnetic field component of the electrogamnetic waves. In the phase shifter constructed in accordance with the present invention substantially the entire volume of the ferrimagnetic material of a toroid inter acts in the desired manner with the electromagnetic waves thus permitting toroids of minimum size to be employed to obtain a given value of differential phase shift.

It therefore is an object of this invention to provide a latching-type digital phase shifter that is small in size and efficient in operation.

Another object of this invention is to provide a reciprocal digital phase shifter that utilizes toroids of gyromagnetic material and achieves optimum interaction of the gyromagnetic material with electromagnetic waves.

The present invention will be described by referring to the accompanying drawings wherein:

FIG. 1 is a simplified illustration of an embodiment of the present invention constructed in double ground plane strip transmission line;

FIG. 2 is an illustration of a toroid of ferrimagnetic material employed in the device illustrated in FIG. 1 and illustrates the magnetizing and demagnetizing flux paths in the toroids;

FIG. 3 is an illustration of a toroid of ferrimagnetic material showing its direction of magnetization relative to the magnetic field lines of the electromagnetic waves in a TEM mode transmission line;

FIG. 4 is an illustration of a rectangular waveguide embodiment of the present invention; and

FIG. 5 is an illustration of the magnetization of a toroid relative to the magnetic field lines of the electromagnetic waves in a rectangular waveguide.

In accordance with one embodiment of the invention in which the phase shifter is constructed in double ground plane strip transmission line, the center strip conductor of the transmission line is slotted along its length to receive a plurality of rectangularly shaped toroids of ferrimagnetic material. The toroids are symmetrically positioned with the center axes of their apertures transverse to the longitudinal axis of the line and parallel to the surfaces of the ground planes. The toroids are of different sizes and each has a square hysteresis loop magnetization characteristic. Respective pulse current sources are provided to independently magnetize the toroids to one of their remanent magnetization states, as desired. When in their remanent magnetization states, the various toroids introduce different values of phase shift in proportion to their sizes. Means also are provided to selectively demagnetize the individual toroids, in which case the value of phase shift introduced by the respective toroids returns to a reference value. Various values of phase shift may be obtained by selecting different combinations of magnetization states of the toroids. By virtue of the positioning and orientation of the toroids in the transmission line substantially the entire volume of each toroid is magnetized transversely to the linearly polarized magnetic field components of the electromagnetic waves on the transmission line, thereby achieving optimum utilization of the ferrimagnetic material.

Referring now in detail to FIG. 1, the illustrated latching-type digital phase shifter is comprised of strip transmission line which is made up of the two outer broad conductive ground planes 11 and 12 and the narrow center strip conductor 13. Center strip conductor 13 is tapered at both of its ends to form transitions to connect with respective coaxial line connectors, such as connector 15. Strip transmission line 10 propagates electromagnetic waves in a TEM mode in which the electric field extends transversely between the center strip conductor 13 and the respective ground planes 11 and 12. The magnetic field lines of this TEM mode are in the form of ellipses that extend circumferentially about center strip conductor 13, it being well understood that this magnetic field is linearly polarized. Center strip conductor 13 contains the two slots 13 and 19 within which are symmetrically disposed the toroids 22 and 23 of ferrimagnetic material. Toroids 22 and 23 are positioned so that the central axes of their apertures 24 and 25 are transverse to the longitudinal axis of strip line 10 and parallel to the surfaces of the ground planes 11 and 12. Toroids 22 and 23 have square hysteresis loop magnetization characteristics and may be comprised of any of the suitable ferrimagnetic materials that are known to those skilled in the art. In a practical latching-type digital phase shifter intended for use in an electronically scanned radar system more than two toroids most likely would be employed, but for simplicity of illustration and description, just two toroids have been illustrated in FIG. 1.

A magnetizing winding 28 extends from the magnetizing current source 29 through the aperture 24 in toroid 22 and magnetizes the toroid circumferentially in a direction around its toroidal shape, as illustrated in FIG. 2. A demagnetizing winding 31 threads a smaller aperture 32 through the bottom leg of toroid 22 and serves to demagnetize toroid 22, in a manner to be described below. Aperture 32 is located below the center line of the bottom leg of toroid 22 so that more ferrimagnetic material is above it than below it. A second magnetizing winding 34 and a second demagnetizing winding 35 are coupled from magnetizing current source 36 and thread the toroid 23 in the same manner as the windings 28 and 31 thread the toroid 22.

The magnetizing current sources 29 and 36 are connected by the lines 38 and 39 to a current control source, not illustrated, which is capable of activating the sources 29 and 36 to pass magnetizing or demagnetizing current pulses through the corresponding windings that pass through toroids 22 and 23. In practice, each phase shifting device 10 may include four toroids which respectively produce differential phase shifts of 22.5", 45, and By selectively choosing different magnetization states of the four toroids, differential phase shifts in increments of 22.5" can be selected from 0 to 363. The current control source that controls the magnetizing current sources such as 29 and 36 may be under control of logic or computer apparatus which programs the magnetization states of the toroids of all the phase shifters of a radar system to achieve the desired scanning of the antenna beam.

In the operation of a digital phase shifter is it required that the ferrirnagnetic material produce two different values of phase shift when in the two different magnetization states. 'I he different values of phase shift result from the fact that the ferrimagnetic material presents different values of permeability to the electromagnetic waves when in the two different magnetization states. To assure that the phase shifter functions in a reciprocal manner the magnetic fields of electromagnetic waves that propogate in opposite directions through the ferrimagnetic material must be linearly polarized. To add assurance that this condition is in fact achieved in the device of FIG. 1, slabs 53, 54 and 55, 56 of a low loss, non magnetic dielectric material having a relative dielectric constant substantially the same as that of the toroids of ferrimagnetic material are positioned against the sides of toroids 22 and 23. The function served by the dielectric slabs 53, 54 and 55, 5 6 is to present at the sides of the toroids 22 and 23 a medium having the same dielectric constant so that the magnetic field lines of the electromagnetic waves are not disturbed at the side boundaries and thus the field will be substantially purely linearly polarized rather than tending to become elliptically polarized at the boundaries as they would if a different dielectric constant medium were present. Further, for the ferrimagnetic material to interact with the magnetic field of the electromagnetic waves it is necessary that the material be magnetized in a direction transverse to the direction of the magnetic field component of the electromagnetic waves. Should the material be magnetized parallel to the direction of the magnetic field of the electromagnetic waves the magnetic susceptibility of the material will be substantially zero and no permeability change will result from different states of magnetization of the material.

The manner in which a toroid, such as toroid 22, is magnetized and demagnetized will be explained with the aid of FIG. 2. A magnetizing current flowing through winding 28 magnetizes toroid 22 in a circumferential direction, as illustrated by the solid arrows. The toroid 22 has a square hysteresis loop magnetization characteristic so that a magnetizing current pulse through winding 28 establishes the illustrated magnetization, this magnetization being substantially the saturation magnetization of the material. This remanent magnetization will remain after the conclusion of a magnetizing current pulse in winding 28. To demagnetize the toroid 22 a current pulse is passed through the demagnetizing winding 31 which threads the smaller aperture 32 in the bottom leg of the toroid. The demagnetizing current tends to establish a circumferential magnetizing field about the aperture 32, but because the material is substantially at its saturation magnetization in the direction illustrated, very little additional magnetic flux can flow through the narrow bottom portion of the bottom leg below aperture 32 where the demagnetizing flux is in the same direction as the remanent magnetization of the bottom leg. In the top portion of the bottom leg that is above the aperture 32, however, the flux established by the demagnetizing field is in the direction opposite to the remanent magnetization of the bottom leg. The demagnetizing flux therefore opposes the remanent magnetization of the toroid and establishes a counter-acting flux in the clockwise direction, this flux being proportioned to substantially demagnetize the toroid to its zero magnetization state.

The physical orientation of the toroids within the strip transmission line in the manner illustrated in FIG. 1 achieves optimum interaction between the ferrimagnetic material and the electromagnetic waves propagating on the transmission line because, when magnetized, all four legs of the toroid are magnetized in a direction transverse to the direction of the linearly polarized magnetic field component of the electromagnetic waves so that all portions of the ferrimagnetic material will contribute to the desired interaction that produces the phase shift of the eletromagnetic waves. The relationship between the magnetic field component of the waves and the magnetization of a toroid of FIG. 1 is illustrated in FIG. 3. The top and bottom legs of the toroid are magnetized in opposite longitudinal directions, and the front and back legs are magnetized in opposite vertical directions. The magnetic field lines m of the waves are horizontal in the regions occupied by toroid 22 and are transverse to the directions of magnetization of all four legs of the toroid. Because a reciprocal phase shift is desired, the toroids 22 and 23 are centrally positioned in the transmission line to assure that the magnetic field of the electromagnetic Waves is linearly polarized in the regions occupied by the toroids. Any asymmetry in the position of the toroids may tend to destroy the linear polarization of the magnetic field of the electromagnetic wave and this would lead to non-reciprocal operation of the phase shift.

In a device constructed substantially as illustrated in FIG. 1 and using toroids made of rare earth substituted yttrium iron garnet ferrimagnetic material, differential phase shifts of the order of 75 degrees per inch of toroid material have been obtained for devices operating in the C-band of the microwave frequency spectrum.

The above-described manner of positioning the toroids in a TEM mode transmission line to obtain optimum interaction between the ferrimagnetic material and the electromagnetic waves with a minimum amount of material and to minimize the required magnetizing and demagnetizing energy is directly applicable to a rectangular waveguide embodiment of a latching-type digital phase shifter. In FIG. 4, the hollow rectangular waveguide 44 propagates electromagnetic waves in the dominant TE waveguide mode. Toroids 42 and 43 of ferrimagnetic material have square hysteresis loop magnetization characteristics and are centrally positioned within the waveguide midway between the narrow walls in the region where the magnetic field of the TE mode waves is linearly polarized. The windings 45 and 46 pass through the respective slits 47 and 48 in the toroids 42 and 43 and carry both the magnetizing and demagnetizing currents from the respective sources 54 and 51. DC. current pulses through the windings 45 and 46 will magnetize toroids 42 and 43 to one of their remanent magnetization states in circumferential directions around the slits 47 and 48. In this embodiment of the invention the other magnetization states for the toroids will be their unmagnetized states. The toroids may be demagnetized by a demagnetizing current in the form of a rapidly decaying oscillatory current from the respective sources 50 and 5.1. The demagnetizing means illustrated in FIG. 2 also could be used if desired and may be preferred in many instances since it ordinarily requires less energy from the current source. Again in this embodiment of the invention, the ferrimagnetic material in all of the four legs of a toroid is magnetized in a direction transverse to thatportion of the magnetic field component of the waves that passes through the toroids. This relationship is illustrated in FIG. 5 wherein the magnetic field lines m of the waves are closed loops that are parallel to the top and bottom walls of the waveguide. These magnetic field lines extend horizontally in the regions occupied by a toroid 42 and are transverse to the directions of magnetizations of the four legs of the toroid.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

1. In an electromagnetic wave device employing a member of gyromagnetic material and operating to have the magnetization state of said member switched between two different magnetization states to effect dilferential interaction with linearly polarized electromagnetic waves when in the two different magnetization states, the combination comprising,

means for propagating electromagnetic waves along a given direction in a propagating mode in which the magnetic field components of the waves are linearly polarized in a given region,

a member of gyromagnetic material having an aperture, said member being disposed entirely within said region and oriented so that an axis of symmetry through the aperture is transverse to said given direction and said aperture being an elongated slot extending in the direction of wave propagation so that the lines of flux established around said axis of symmetry are substantially everywhere orthogonal to said linearly polarized magnetic field contained within said gyromagnetic member,

means for driving said member to a first magnetization state by establishing lines of flux around said axis of symmetry, whereby said member presents a first value of permeability to said waves, and

means for changing the magnetization of said member to a second magnetization state, so that said member presents a different value of permeability to said waves,

said member being alternately switched between said first and second magnetization states.

2. The combination claimed in claim 1 wherein said means for propagating electromagnetic waves comprises,

a hollow conductively bound waveguide that propagates electromagnetic waves in a mode in which the magnetic field is linearly polarized in the central region of the waveguide,

said member of gyromagnetic material being positioned in said central region of the waveguide.

3. The combination claimed in claim 2 wherein said means for changing the magnetization of said member to a second magnetization state comprises,

an additional aperture that extends through said mem ber in a direction parallel to said axis of symmetry, and

an electrical conductor that passes through said additional aperture for establishing a magnetic flux field in a direction to change said first magnetization state.

4. A latching-type digital phase shifter comprising,

a strip transmission line comprised of two parallel spaced broad conductive ground planes and a narrow strip conductor disposed between said planes,

said transmission line extending along an axis and propagating electromagnetic waves in a TEM mode whose magnetic field is linearly polarized in the region of the line adjacent the strip conductor,

a body of ferrimagnetic material having an aperture and a substantially square hysteresis loop magnetization characteristic, said body being disposed entirely within said transmission line in symmetrical relationship to said strip conductor and oriented such that an axis of symmetry through its aperture extends transversely to the transmission line axis and parallel to said ground planes,

means for magnetizing said body to a first remanent magnetization state by establishing lines of fiux around said axis of symmetry, and

means for changing the magnetization of said body to a state other than the second remanent magnetization state, associate-d with the hysteresis loop of said first magnetization state,

said member being alternately switched between said first and second magnetization states.

5. The combination claimed in claim 4 and further including,

a plurality of additional bodies of ferrimagnetic material each having an aperture and being successively disposed along said strip conductor in a manner substantially identical to that of the first-described member,

means for independently magnetizing each one of said additional bodies to its first remanent magnetization state by establishing lines of flux around its aperture, and

means for independently changing the magnetization state of each one of said bodies to a state other than the second remanent magnetization state associated with the hysteresis loop of said first magnetization state.

6. The combination claimed in claim 4 wherein the means for magnetizing said body to a first remanent magnetization state comprises,

a first electrical conductor that passes through said aperture of said body, and

means for passing a magnetizing current through said electrical conductor.

7. The combination claimed in claim 4 wherein the means for changing the magnetization of said body comprises,

an additional aperture that extends through said body in a direction parallel to said axis of symmetry, and

a second electrical conductor that passes through said additional aperture.

8. The combination claimed in claim 7 wherein said additional aperture is closer to the periphery of said body.

References Cited UNITED STATES PATENTS 3,051,917 8/1962 Gyorgy et al. 333 a1 3,079,570 2/1963 Hickey 333-241 3,274,521 9/1966 Nourse 333 24.1 3,277,401 10/1966 Stern 333 24.1

HERMAN KARL SAALBACH, Primary Examiner.

P. L. GENSLER, Assistant Examiner. 

1. IN AN ELECTROMAGNETIC WAVE EMPLOYING A MEMBER OF GYROMAGNETIC MATERIAL AND OPERATING TO HAVE THE MEGNETIZATION STATE OF SAID MEMBER SWITCHED BETWEEN TWO DIFFERENT MAGNETIZATION STATES TO EFFECT DIFFERENTIAL INTERACTION WITH LINEARLY POLARIZED ELECTROMAGNETIC WAVES WHEN IN THE TWO DIFFERENT MAGNETIZATION STATES, THE COMBINATION COMPRISING, MEANS FOR PROPAGATING ELECTROMAGNETIC WAVES ALONG A GIVEN DIRECTION IN A PROPAGATING MODE IN WHICH THE MAGNETIC FIELD COMPONENTS OF THE WAVES ARE LINEARLY POLARIZED IN A GIVEN REGION, A MEMBER OF GYROMAGNETIC MATERIAL HAVING AN APERTURE, SAID MEMBER BEING DISPOSED ENTIRELY WITHIN SAID REGION AND ORIENTED SO THAT AN AXIS OF SYMMETRY THROUGH THE APERTURE IS TRANSVERSE TO SAID GIVEN DIRECTION AND SAID APERTURE BEING AN ELONGATED SLOT EXTENDING IN THE DIRECTION OF WAVE PROPAGATION SO THAT THE LINES OF FLUX ESTABLISHED AROUND SAID AXIS OF SYMMETRY ARE SUBSTANTIALLY EVERYWHERE ORTHOGONAL TO SAID LINEARLY POLARIZED MAGNETIC FIELD CONTAINED WITHIN SAID GYROMAGNETIC MEMBER, MEANS FOR DRIVING SAID MEMBER TO A FIRST MAGNETIZATION STATE BY ESTABLISHING LINES OF FLUX AROUND SAID AXIS OF SYMMETRY, WHEREBY SAID MEMBER PRESENTS A FIRST VALUE OF PERMEABILITY TO SAID WAVES, AND MEANS FOR CHANGING THE MAGNETIZATION OF SAID MEMBER TO A SECOND MAGNETIZATION STATE, SO THAT SAID MEMBER PRESENTS A DIFFERENT VALUE OF PERMEABILITY TO SAID WAVES, SAID MEMBER BEING ALTERNATELY SWITCHED BETWEEN SAID FIRST AND SECOND MAGNETIZATION STATES. 